Joint construction for combustion chamber casings



June X8, 1957 J. T. PURvls ETAL 2,795,930

JOINT CONSTRUCTION FOR COMBUSTION CHAMBER CASINGS Filed Dec. 6, 1951 2 Sheets-Sheet 1 IPI/WIS June 18, 1957 1 T pURVls ETAL 2,795,930

JOINT CONSTRUCTION FOR COMBUSTION CHAMBER CASINGS Filed Deo. 6, 1951 2 Sheets-Sheet HTTUHNfY JOINT CONSTRUCTION FOR COMBUSTION CHAMBER CASINGS Joseph Thompson Purvis, North York Township, York County, Ontario, and Lloyd Calvin Secord, Toronto, ntario, Canada, assignors to A. V. Roe Canada Limited, Malton, Ontario, Canada, a corporation Application December 6, 1951, Serial No. 260,262' 4 Claims. (Cl. 60-39.31)

This invention relates to the combustion chambers of gas turbine enginesand particularly to the construction of the casingsthereofl A common form of combustion system of a-gasturbine engine comprises a group of tubular combustion chambers arranged annularly aroundvand parallel to the longitudii nal axis of the engine. Each combustion chamber contains a ame tube situated coaxially and in spaced rela:- tionship to the casing of the chamber, the purpose ofthe ilame tube being to contain the burning' gases while alayer of insulating'and cooling air llows in the annular space between the flame tube and the casing. A combustion chamber casing commonly has a substantially cylindrical central portion and terminal portions taperingat the forward end to the 'attachment of the chamber to the diffuser casing of the engine, and at the rearwardend to the attachment of the casingto the turbine nozzle box. Since the diameters of the combustion chamber at its attachment to the diffuser casing and at its attachment tothe nozzle box are each materially less than the maximum diameter of the flame tube, it is necessary to incorporate a joint in the combustion chamber casing -so that the llame tube may be inserted therein.

The overall diameter of the engine is usually deter'- mined by the overall diameter of the combustion system and it is desirable that adjacent combustion chambers should be mounted as closely to each other as possible, particularly in the application of the engine to aircraft. For this reason any avoidable'excrescences on the perimeters ofthe combustion chambers should `be eliminated so that for a given diameter of each combustion chamber, the overall diameter of the combustion sys-tem may be held to a minimum.

It is the object of this invention to provide a combustion chamber casing incorporating a joint which will furnish an opening sufliciently large to enable the flame tube to be inserted, 4and characterized by the absence of undesirable excrescences on the outside of the casing. Other objects and advantages will be apparent from the following description.

In the attached drawings forming a part of this application and in which like reference characters designate like parts throughout the same,

Fig. l is a side elevation of a gas turbine engine partially cut away to show a combustion chamber casing and a ame tube installation;

Fig. 2 is a longitudinal section of a combustion charnber taken on an axial plane of the engine;

Fig. 3 is an end elevation of a combustion chamber viewed in the direction of the arrow A in Fig. 2;

Fig. 4 is a fragmentary cross-sectional view of the joint in the combustion chamber which is the subject of this invention; and

Fig. 5 is a fragmentary perspective view of the joint, showing the clamp ring immediately prior to interdigitation with the castellations on the tlange rings of the joint.

The engine shown in Fig. 1 includes a compressor 1t) and a combustion system comprising six annularly ar- 2,795,930 Patented June 18, 1957 ranged combustion chambers 11` which discharge into a turbine 12; the exhaust gases from the turbine issue as apropulsive jet froma tail cone 13; Each` combustion [chamber has a casing 14 and a am'e tube 15 situated within the'casing in spaced relationship thereto. The llame tubes are interconnected -by interconnector tubes 16.

The casing 14 comprises a cylindrical central portion 14e, anintegral'upstr'eam terminal portion 14h providing aninlet end and'tapering to the'attachment ofthe casing 14 to a diffuser 17, and a downstream terminal portion 14c and providing an outlet endI and tapering to the at*- tachment of the casing 14 to a nozzle-box 18; The flame tube 15 is mounted within the casing 14, inspaced relationship thereto, by three supports 19 '(of which only one is shown in'Fig. 2) adjacent the upstream-end of the flame tube and by a spigot mounting 20 at the downstream end where-the chamber is attached to the'nozzle box. Two of-thesupports 19 are superimposed upon the ports 21 and provide-the attachments of the interconnector tubes 16; whereby the flame tubes of adjacent chambers are interconnected through their respective ports 21.

The flame tube is composed of a series of overlapping sections of progressively increasing diameter, including a substantially conical inlet section 15a, a cylindrical intermediate section 15b, and an outlet lsection 15G. The diameter of the outlet section 15C increases immediately downstream'of the joint between-this-section andthe preceding sectionslb, attaining a maximum at the station indicated by reference numeral 22; and thereafter decreases towards thespigot mounting 20; Other details of the construction of the flame tube are not of significance 'to this invention which is primarily concerne'd'with themaximum diameter of thellame tube at the station 22 and the' construction of the casing to provide'a means for installingfthe ame tube within the casing.

According to the invention a joint 23-is providedin the downstream terminal'portion 14' near thel central cylin drical portion 14a of the casing 14, with a coupling assembly, generally indicated by the numeral 24, for-securing the resulting fixed and removable parts of the terminaly portion 14 together. A cross-section of the coupling.f assembly 24 is shown in Fig; 4 from whichit will be seen-that it comprises a flange ring 25A attached to the casing-14a and-providing a fixedl part of the terminal portion 14c andanother flange ring 26 attached to and providing a continuation of the removable part of the'terminal portion 140, the two rings being held in abutment bythe clamp ring 27 and providing abutting annular anges 25a and 26a. The inside diamete-r of the llange ring 25 is just sufficient to enable the flame tube, at its station 22, to 'pass through it and the outer configuration of the coupling assembly is such'that its overall outside diameter is not materially greater than the outside diameter of the cylindrical central'p'ortion 148V ofthe casing..l Becausethe ange ring 25 is kof relatively thinl material, like the rest of the casing, the annular width'of the ilanges 25a a-nd 26a will be materially greater than the maximum thickness of the wall of the fixed part.

The lixedpart ofthe terminal portion 14, formed'by the flange ring 25, is tapered toward its downstream end, for instance by being joggled inwardly as shown in the drawings, and thus its cross-sectional outer dimensions diminish downstream toward the joint to accommodate the added wall thickness at the joint within the outside diameter of the central portion 14a of the casing. At its downstream end a group of equally spaced castellations 25D are disposed around the periphery of the flange 25a on the flange ring 25. A second group of castellations 26b adapted to register with the first group are similarly provided on the liange 26a. `In the assembled position the castellations 25b and 26b are clamped together in registering abutment by a cylindrical assembly of annularly spaced J -section clamps 27a provided by the clamp ring 27. The circumferential width of the clamps, being less than the spaces between the castellations, and their spacing on the clamp ring `are such that, during assembly, the clamps are interdigitated with the castellationsA and then brought to bear on the mating castellations by a small angular rotation of the clamp ring. Each clamp 27a is provided with a hook portion 27b which engages a castellation h, and with a screw 28, which engages the corresponding castellation 26b and which, when tightened, clamps the castellations in mutual abutment.

An annular spigot 29 is provided on the ange 258 to engage a corresponding annular recess in the ilange 26a to centralize the downstream terminal portion 14c of the casing with the cylindrical portion 14a and the joint is rendered gastight by the gasket 30 housed in an annular groove between the abutting joint surfaces of the two llanges 2Sa and 26a.

It will be understood that the clamps need not necessarily be incorporated as integral parts of a clamp ring and that the construction of the coupling assembly is not substantially altered by the use of individual clamps, which can be applied independently of one another. The essential feature of the coupling assembly is the situation of the actual mating surfaces of the tlange rings downstream of the greatest diameter of the combustion chamber casing so that the annular thickness of the coupling assembly, including the clamp, is accommodated on the taper of the downstream terminal portion and substantially within the annulus defined by the outer diameter of the casing and the maximum diameter of the flame tube at station 22. In some instances it may be possible to use a conventional bolted llange joint, in place of the coupling arrangement described, but normally the annular space available will not provide suflicient edge distance between the bolt holes and the periphery of the flange rings.

The construction herein shown and described is therefore to be taken as a preferred example of the application of the invention and various changes in the shape, size and arrangement of the parts may be resorted to without departing from the spirit of the invention or the scope of the subjoined claims.

What we claim as our invention is:

1. In a gas turbine engine having a llame tube disposed within a combustion chamber, an open-ended tubular casing for the combustion chamber spaced from the llame tube and comprising a central casing part, terminal casing parts tapering generally from the central part to the ends of the casing, the cross-sectional inner dimensions of the open ends of the terminal casing portions being less than the maximum corresponding dimensions of the llame tube whereby the latter is prevented from passing through the said end openings, one of the ter- `minal parts having a joint longitudinally spaced from the central casing part and providing a fixed part secured to the central part and a removable part, the crosssectional outer and inner dimensions of the xed part diminishing toward the joint, coupling means for removably securing together the said iixed and removable parts and projecting outwardly from the outside of the xed part, the annular width of the coupling means being materially greater than the thickness of the walls of the xed part, the cross-sectional dimensions of the casing at the said joint being greater than the maximum corresponding dimensions of the flame tube whereby the latter may be inserted in the casing when the said removable part is removed, and the cross-sectional outer dimensions of the coupling means being not substantially greater than the corresponding outer dimensions of the central casing part whereby the coupling means may be accommodated within a hypothetical longitudinal extension of the periphery of the central casing part.

2. The combination claimed in claim 1 in which the coupling means include outwardly extending flanges on each of the said two parts at the said joint providing clamp-receiving surfaces, and also include clamp means external of the casing and llanges, the clamp means engaging the said surfaces and removably securing together the said two parts.

3. The construction claimed in claim 2 in which each of the anges has an annular joint surface facing the other flange and an outwardly extending element registering with that on the other ilange, one of the said llanges having a spigot extending from the joint surface thereof and the other of said flanges having a recess in its joint surface thereof, and the said clamp means include a clamp embracing the said element to secure the said two parts togetherwith the joint surfaces in sealing contact and the spigot extending into the said recess, the taper of the said fixed part providing a reduction in diameter of the casing between the central casing part and the said joint to .accommodate the annular thickness of the said ilanges and clamp, the maximum cross-sectional dimensions of the said llanges and clamp being not substantially greater than the outer diameter of the central casing part.

4. A combination `as claim in claim 2 in which each of the ilanges has a series of outwardly extending spacedapart castellations registering with those on the other flange, and in which the clamp means comprises a substantially cylindrical clamp ring having a series of spacedapart clamps disposed around its circumference and encircling the casing adjacent the said joint, each of the clamps embracing a registering pair of the castellations to secure the said two parts together with the llangcs in sealing contact.

References Cited in the file of this patent UNITED STATES PATENTS 662,907 Boeklen Dec. 4, 1900 735,221 Duord Aug. 8, 1909 924,039 Clark June 8, 1909 1,080,825 lFryer Dec. 9, 1913 1,162,362 Hyland Nov. 30, 1915 1,475,150 Sweney Nov. 20, 1923 2,105,022 Wilson et al Ian. 1l, 1938 2,432,359 Streid Dec. 9, 1947 2,547,619 Buckland Apr. 3, 1951 2,592,060 Oulianoi Apr. 8, 1952 2,625,792 McCarthy et al. Jan. 20, 1953 2,670,600 Owner et al Mar. 2, 1954 2,692,478 Hill Oct. 26, 1954 FOREIGN PATENTS 621,438 Great Britain Apr. 8, 1949 

